Position indicating electrical switch unit

ABSTRACT

A mechanically operated switch unit having an electrical snap action switch in which the switching is effected in an hermetically sealed atmosphere but yet the unit has a removable cover to enable adjustment and/or repair in the field. The switch is protected from excessive movement which could destroy it by having the actuator movement structurally limited and by operating the switch inversely so that it is normally closed when not actuated, the latter also making the unit essentially free from vibration actuation.

United States Patent Robert R. Hellman Bridgeport, Conn.

Dec. 22, 1969 June 15, 1971 Westport Development & ManufacturingCompany, Inc.

Milford, Conn.

Inventor Appl. No. Filed Patented Assignee POSITION INDICATIN GELECTRICAL SWITCH UNIT 8 Claims, 5 Drawing Figs.

US. Cl 200/168, 200/ l 67 Int. Cl Hl0h 9/04 Field of Search 200/168A-168 G, 167 R [56] References Cited UNITED STATES PATENTS 2,206,8827/1940 Davis 200/168 (C) X 2,633,520 3/1953 Chandler et a1. 200/168 (D)2,862,084 11/1958 Russell 200/168 (A) 3,158,703 11/1964 De Smidt..200/168 (G) (UX) FOREIGN PATENTS 1,084,345 6/1960 Germany 200/168 (G)Primary Examinerl-l. 0. Jones Attorney-Johnson and Kline ABSTRACT: Amechanically operated switch unit having an electrical snap actionswitch in which the switching is effected in an hermetically sealedatmosphere but yet the unit has a removable cover to enable adjustmentand/or repair in the field. The switch is protected from excessivemovement which could destroy it by having the actuator movementstructurally limited and by operating the switch inversely so that it isnormally closed when not actuated, the latter also making the unitessentially free from vibration actuation.

POSITION INDICA'IING ELECTRICAL SWITCH UNIT The position indicatingswitch unit herein disclosed has particular utility when used to providean electrical signal indicating whetheror not a movable structure is ata particular position. One such structure could be the landing gear ofan aircraft and the switch unit is utilized to provide a signal that awheel is either down or up by the switch being positioned to bemechanically operated in one of these positions. In such a use, it isalso required that the switch be rendered unaffected by or effectenvironmental conditions and hence the switches are made to behermetically sealed. Such sealing in heretofore suggested unitsprevented maintenance of the unit by fieldpersonnel with the result thata complete unit was replaced when necessary rather than attempt repairsor adjustment on the unit. The replacement of a complete unit caused thesubstitution to be quite expensive as opposed to replacing just themalfunctioning part or adjusting the unit while it was in place.Moreover, attempts to provide adjustment of operation in the unit in thefield, had required additional exterior adjusting mechanism whichcooperated with the switch and, while enabling adjustment made the unitquite expensive and complex.

It is accordingly an object of the present invention to provide aposition indicating electrical switch unit in which the switching iseffected in an hermetically sealed environment but yet in which the unitis capable of being repaired and/or adjusted in the field withoutdestroying the seal.

Another object of the present invention is to achieve the above objectwith a switch unit which is relatively economical to manufacture,capable of withstanding relatively large mechanical forces withoutdetriment and durable in use.

A further object of the present invention is to provide a positionindicating electrical switch unit that achieves the above objects andmay be easily repaired or adjusted by field personnel but yet which issubstantially incapable of being inadvertently destroyed by saidpersonnel.

In carrying out the present invention, the herein disclosed switch unitincludes a body having a web formed with spaced apart flanges. A plungerassembly is mounted on one flange and has a portion extending outwardlyof the unit to be operated by a movable structure whose position isdesired to be indicated by the unit. Supported on the other flange is anelectrical connector to which exterior wiring may be connected and thesignal utilized.

Mounted on the web portion is an hermetically sealed snap action switchsuch as disclosed in my U.S. Pat. No. 3,431,378 and assigned to theassignee of the present invention. The switch is of the snap actionmovable blade type and the switching components are contained within anhermetically sealed casing with an operating arm effecting actuation ofthe switch through the casing.

The plunger assembly includes a plunger that is connected to theactuating arm such that in one position of the plunger the switch isnormally open while in another position the switch is held closed. Theplunger is normally biased outwardly to cause the switch to be held inits closed position but when the movable structure forces the plungerinwardly it frees the actuating arm for movement and the switch moves toits normally open position. The movement of the switch from a normallyclosed to a normally open position provides a different connection inthe switch terminals which effectively constitutes an electrical signalas the term is herein used.

The plunger includes a rod that is supported by the web and a link whichengages the actuating arm of the switch. The switch if fixedly mountedon the web and to permit adjustment of the actuation point of theswitch, the link is connected to the rod to be adjustable along thelength of movement of the rod. A cover consisting essentially of arelatively thin sheet metal can covers the switch and the actuating linkand accordingly extends from one flange to the other. However, the coveris removable to permit access to the switch exterior and the adjustablelink to thereby enable adjustment by field personnel even when theswitch is mounted and in use.

A cap is connected to the cover to complete the switch enclosure andsupports an operating button having an exterior projection which servesto transmit switch operating motion to the plunger assembly. The extentof outward movement of the plunger assembly is controlled by the buttonengaging a surface of the cap while the inward movement of the plungerassembly is controlled by the plunger abutting the adjacent flange ofthe body. Thus the outward movement ofthe plunger assembly which causedthe switch to be held at its normally closed position is closelycontrolled to prevent extended overtravel of the switch actuator armwhile the inward movement of the plunger to enable actuation of theswitch to its normally open position is limited by the plunger assemblyengaging a rigid flange. Moreover, as the inward movement is a releasingmovement of the switch substantial plunger travel is permissible withoutharm to the switch.

Other features and advantages will hereinafter appear.

in the Drawings:

FIG. 1 is a substantially axial section of the position indicatingelectrical switch unit of the present invention, somewhat enlarged.

FIG. 2 is a partial section taken on the line 2-2 of FIG. 1.

FIG. 3 is a plan view, somewhat reduced.

FIG. 4 is a section taken on the line 4-4 of FIG. 1.

FIG. 5 is a section taken on the line 5-5 of FIG. 1.

Referring to the drawing, the position indicating electrical switch unitof the present invention is generally indicated by the reference numeral10 and includes a pair of electrical snap action switches 11 and 12though it will be understood that only one may be utilized if desired.The switches 11 and 12 are identical and of the type shown in myabove-noted U.S. patent. Each is contained within an hermetically sealedcasing and has an actuating arm extending outwardly therefrom so thatmovement of the arm will effect operation of its associated switch. Thearm for the switch 12 is indicated by the reference character 13.

The unit includes a unitary body 14 having a first flange l5 and asecond flange 16 disposed on opposite ends of a web portion 17. Screws18 extend through the switches 11 and 12 and thread into the web portion17 to hold the switches in fixed relation to the body.

The second flange 16 is formed with a rectangular cutout 19 on its outersurface which receives a rectangular flange 20 of a typical pin-typeelectric connector 21. Rivets 22 extend through the flanges l6 and 20 tosecure the connector 21 to the body. The connector 21 is of essentiallyconventional construction having an exterior threaded portion 23 andcontact pins 24' supported therewithin and is adapted to be secured to amating connector that is attached to an external multiwire cable. Theflange 16 has a circular cutout 25 to receive the inner portion 26 ofthe connector 21 with wires 27 extending from the three switch terminalsto the inner ends of the pins. For sealing the connection between thewires and the switch terminals they are preferably covered by a hardenedepoxy such as shown as 28.

The plunger assembly for operating the switches 11 and 12 includes anhexagonal rod 29 which extends through an aperture 30 formed in the bodyto terminate in a lower threaded end 31. A flat link 32 is mounted onthe threaded end 31 by a pair of nuts 33.

The flat link 32 extends to have its end portions engage the actuatorarms of the switches 11 and 12 and is moved along the axis of the rod29. Additionally, plates 34 and 35 are supported on the web by thescrews 18 with each of the plates having a cutout 36 through which theends of the link 32 extend in order to prevent rotation of the link. Theweb 17 is cut out as at 37 to permit the link 32 to extend outwardlytherefrom and also to permit access to the adjusting nuts 33.

The upper end of the rod 29 extends from the first flange l5 and isthreadedly connected to a disc 38. Positioned between the disc 38 andthe first flange is a spring 39 that is under compression and isutilized to urge the plunger assembly outwardly. The inward movement ofthe assembly is limited by the inner surface of the disc 38 engaging asurface 40of the first flange 15.

The first flange 15 is formed with an exteriorly threaded portion 41which threadingly mates with a cap 42. An actuator button 43 issupported for axial movement in the cap 42 by an annular bearing 44 andincludes a projecting portion 45 that extends beyond the cap. The button43 further includes an enlarged circular portion 46 that is formed toprovide a somewhat spherical lower surface 47 which engages the flatupper surface of the disc 38. The upper surface of the portion 46 isformed with an annular flange 48 that engages the interior of the cap.

A substantially cylindrical cover 49 has one end formed to provide anout-turned lip 50 by which it may be secured to the cap 42 as by screws51. The other end of the cover 49 is formed to provide an in-turned lip52 which abuts the exterior of the second flange 16. Preferably anO-ring 53 is inserted therebetween to effect a dust tight connection.

The cover 49 essentially protects the switch from dust and physical harmbut yet does not effect an hermetic seal. The cover may easily beremoved by unscrewing the screws 51 and with its removal, the operatingportions of the switch may be adjusted, inspected, tested or replacedwithout destroying the hermetic sealing of the contacts of the switches11 and 12 wherein the switching action occurs.

The spring 39 urges the plunger assembly outwardly until there isengagement between the flange 48 and the interior of the cap 42 at thesurface indicated by the line 54. The extent of outward movement of theplunger is accordingly limited and may be closely controlled and alsothe extent of movement of the link 37 on the actuating arms of theswitches are closely controlled. Accordingly, the overtravel movement ofthe actuating arms is positively controlled and limited to that which isless than could cause detriment to the switches. Movement of the plungerassembly inwardly caused by the structural movement to be sensed on theprojecting portion 45, is limited by engagement of the surface 40 by thedisc 38 and thus further inward movement of the plunger is accordinglyalso closely controlled. With such an actuating movement, the link 32will move downwardly permitting the switch arms 11 and 12 to assumetheir normally open position to which they are conventionally biased andwhere they will remain until the spring 39 is capable of again urgingthe plunger assembly outwardly by removal of the actuating force on thebutton 43. As the inward movement of the plunger is effectivelypretravel movement to the switches, a substantial movement is permittedas pretravel movement will not cause harm to the switches. Moreover, byhaving the switches maintained in their normally closed position by thespring 39, the switches are exceedingly resistant to being actuated byvibration.

As shown in FIG. 3, the cap 42 may be formed to have a rectangularperiphery with holes 55 formed therein for permitting the switch to bemounted in a position on a structure where it will cause the button 43to be located to be actuated by a movable member. The switch willaccordingly provide an electrical signal of the position of the memberby the member causing the plunger to be forced inwardly to shift theconnection in the switches from normally closed to a normally openposition.

When the switch unit is mounted by use of the holes 55 in use, removalof the cover may be effected by fleld personnel by removing the screws51 without requiring the removal of the whole unit. The actuatinglocations of the switches 11 and 12 may then be adjusted by movement ofthe nuts 33. Also, the different parts of the switch unit may then beinspected and/or repaired as they are rendered accessible.

The engagement of the somewhat spherical surface 47 of the button andthe flat surface of the disc tends to permit the button to haverotational movement during its actuation to maintain its free movement.Moreover, the annular flange 48 provides clearance of the remainder ofthe upper surface of the button from the cap and tends to prevent dirtfrom causing cocking of the actuator button. The particular arrangementof the button and plunger assembly as hereinbefore disclosed has beenfound to render the switch of the present invention relativelyeconomical to manufacture without decreasing the positiveness ofactuation by reason of the parts being capable of accommodatingmanufacturing tolerances without introducing misalignment which couldcause binding between the parts.

It will accordingly be understood that there has been disclosed aposition indicating electrical switch unit which is capable of providingan electrical signal indicative of the position of a movable structure.The unit utilizes a snap action switch that is contained within anhermetically sealed atmosphere with the, remainder of the unit beingunsealed to be accessible for adjustment, repair or part replacement byfield personnel without affecting the sealing. Moreover, the unit isconstructed and arranged to limit movement effecting the switch to arange which is not capable of causing harm to the switch.

Variations and modifications may be made within the scope of theinvention and portions of the improvements may be used without others.

lclaim:

1. A position indicating electrical switch unit comprising a body formedto have a web extending between two spaced flanges, an electrical switchhaving an hermetically sealed case and an actuating ann extendingtherefrom with the actuating arm in one position causing closing of theswitch and in another position causing opening of the switch, anelectrical connector secured on one of the flanges, means electricallyconnecting the connector and the switch, means mounting the switch onthe web between the flanges, switch actuating means supported by thebody including a projecting portion extending outwardly from the otherflange and an actuating arm engaging portion whereby movement of theprojecting portion effects the shifting of the switch from one positionto the other and a cover removably mounted on the body and covering atleast said engaging portion and switch.

2. The invention as defined in claim 1 in which the actuating arm isbiased to its open position and in which there are means for urging theswitch actuating means to cause said switch to be at its closed positionwhere said switch is normally maintained in theabsence of forciblemovement of the switch actuating means from its closed position.

3. The invention as defined in claim 2 in which the body includes aremovable cap mounted on the other flange through which the projectingportion extends and is mounted for movement toward and away from thebody and in which there are means for limiting the outward movement ofthe switch actuating means and hence the overtravel movement of theactuating arm by engagement with the cap.

4. The invention as defined in claim 3 in which there are means on saidother flange for limiting inward movement of the switch actuating means.

5. The invention as defined in claim 3 in which the switch actuatingmeans includes a rod positioned in an aperture formed in the web forlongitudinal movement and having one end connected to arm engagingportion, connecting means being adjustable longitudinally of the rod toenable adjustment of the engaging portion with respect to the rodsposition.

6. The invention as defined in claim 5 in which the other end of the rodextends beyond the other flange, an abutment member secured on the otherend of the rod and a surface formed on said flange for engaging theabutment member to limit the inward switch opening movement of the rod.

7. The invention as defined in claim 5 in which the other end of the rodextends beyond the other flange, an abutment member secured on the otherend of the rod, spring means urging the abutment member and rodoutwardly to a switch closing position, the projecting portion includesan inner portion within the cap engageable with the abutment member andin which the means for limiting the outward movement includes the innerportion engaging the cap.

8. The invention as defined in claim 7 in which the engagement betweenthe inner portion and the abutment member includes a pair of surfaceswith one surface being essentially flat and the other surface beingessentially spherical.

1. A position indicating electrical switch unit comprising a body formedto have a web extending between two spaced flanges, an electrical switchhaving an hermetically sealed case and an actuating arm extendingtherefrom with the actuating arm in one position causing closing of theswitch and in another position causing opening of the switch, anelectrical connector secured on one of the flanges, means electricallyconnecting the connector and the switch, means mounting the switch onthe web between the flanges, switch actuating means supported by thebody including a projecting portion extending outwardly from the otherflange and an actuating arm engaging portion whereby movement of theprojecting portion effects the shifting of the switch from one positionto the other and a cover removably mounted on the body and covering atleast said engaging portion and switch.
 2. The invention as defined inclaim 1 in which the actuating arm is biased to its open position and inwhich there are means for urging the switch actuating means to causesaid switch to be at its closed position where said switch is normallymaintained in the aBsence of forcible movement of the switch actuatingmeans from its closed position.
 3. The invention as defined in claim 2in which the body includes a removable cap mounted on the other flangethrough which the projecting portion extends and is mounted for movementtoward and away from the body and in which there are means for limitingthe outward movement of the switch actuating means and hence theovertravel movement of the actuating arm by engagement with the cap. 4.The invention as defined in claim 3 in which there are means on saidother flange for limiting inward movement of the switch actuating means.5. The invention as defined in claim 3 in which the switch actuatingmeans includes a rod positioned in an aperture formed in the web forlongitudinal movement and having one end connected to arm engagingportion, connecting means being adjustable longitudinally of the rod toenable adjustment of the engaging portion with respect to the rod''sposition.
 6. The invention as defined in claim 5 in which the other endof the rod extends beyond the other flange, an abutment member securedon the other end of the rod and a surface formed on said flange forengaging the abutment member to limit the inward switch opening movementof the rod.
 7. The invention as defined in claim 5 in which the otherend of the rod extends beyond the other flange, an abutment membersecured on the other end of the rod, spring means urging the abutmentmember and rod outwardly to a switch closing position, the projectingportion includes an inner portion within the cap engageable with theabutment member and in which the means for limiting the outward movementincludes the inner portion engaging the cap.
 8. The invention as definedin claim 7 in which the engagement between the inner portion and theabutment member includes a pair of surfaces with one surface beingessentially flat and the other surface being essentially spherical.